1. Field of the Invention
The present invention relates to a busbar holding structure.
2. Description of the Related Art
In vehicular battery packs that are connected to a power conversion device for driving a motor in such vehicles as hybrid vehicles and electric vehicles, a battery module is constructed in such a manner that a number of battery cells are oriented in opposite directions alternately and arranged side by side and placed on each other so that each of their positive terminals is adjacent to two negative terminals. Plural battery cells are connected to each other in series or in parallel by connecting the adjoining opposite-polarity electrode terminals of adjoining battery cells by a connection member such as a busbar.
To assemble a battery module having the above configuration, it is necessary to connect adjoining electrode terminals by a busbar at plural locations. To this end, a busbar module is used in which busbars are housed in busbars housing units (the number of which is determined according to that of electrode terminals to be connected to each other) of a wires routing body made of an insulative resin.
A busbar module is proposed which includes plural busbars fixing units (busbars housing units) capable of fixedly housing plural respective busbars while securing positioning etc. of the busbars (refer to JP-A-2004-31049, for example). As shown in FIG. 5A, this conventional busbar module is includes plural busbars fixing units 502 which fixedly house plural respective busbars 501.
As shown in FIG. 5B, each busbar 501 is formed so as to be able to connect adjoining batteries in series when fixedly housed in a busbar fixing unit 502. The busbar 501 has a pair of battery connection holes 503 which are circular through-holes. The pair of battery connection holes 503 are portions through each of which a stud-bolt-shaped electrode is to be inserted. Portions around the battery connection holes 503 are to be sandwiched between the nuts and battery electrode top surface, respectively.
As shown in FIG. 5C, the busbar fixing unit 502 has a bottom wall 507 having a rectangular outline and a frame-shaped side wall 508 which is continuous with the peripheral edge of the bottom wall 507. The bottom wall 507 is formed with a pair of openings 509 and a central receiving portion 510. The pair of openings 509 are portions corresponding to the respective battery electrode top surfaces. The central receiving portion 510 is located between the pair of openings 509 and shaped like a bridge so as to be able to receive a central portion of the busbar 501.
The side wall 508 is composed of a pair of longer side walls 513 which are parallel with the busbar longitudinal direction and a pair of shorter side walls 514 which are perpendicular to the busbar longitudinal direction, and is formed so as to conform to the outline of the busbar 501. Each of the pair of longer side walls 513 is formed with a pair of nail-shaped busbar lock projections 515 which project inward to a small extent. The pair of busbar lock projections 515 is formed at the same position as the central receiving portion 510 in the busbar longitudinal direction so as to be spaced from the central receiving portion 510 in the wall height direction by the thickness of the busbar 501.
To fixedly house the busbar 501 in the busbar fixing unit 502, the busbar 501 is pushed into the inside space of the side wall 508 of the busbar fixing unit 502 and fixed so as to be sandwiched between the central receiving portion 510 and the two pairs of busbar lock projections 515. Peripheral portions of the busbar 501 are received by the bottom wall 507 and the busbar 501 is surrounded by the side wall 508, whereby the busbar 501 is held fixedly without play.
Incidentally, the busbar 501 carries current in a state that its portions around the pair of battery connection holes 503 are sandwiched between nuts and the battery electrode top surfaces, respectively. Thus, the busbar fixing unit 502 is configured so that the battery electrode top surfaces are inserted in the respective openings 509 of the bottom wall 507. Furthermore, in the busbar fixing unit 502, the bottom wall 507 receives the peripheral portions of the busbar 501 and the side wall 508 surrounds the busbar 501, whereby the busbar 501 is held fixedly without play.
As a result, the sizes of the busbar 501 and the busbar fixing unit 502 are large and hence the above conventional busbar module tends to suffer a high manufacturing cost and a heavy weight.
Furthermore, when the busbar 501 is fixedly housed in the busbar fixing unit 502, the busbar 501 needs to be pushed into the inside space of the side wall 508 while the two pairs of busbar lock projections 515 which are provided in the pair of longer side walls 513 are deformed outward elastically. This requires strong force for inserting the busbar 501, resulting in low work efficiency.